1. Field of the Invention
This invention relates to non-contact, in-situ diagnostics used to monitor various thin film growth parameters during multi-sample deposition on high speed rotation stages.
2. Related Art
Essential components for electronic and optoelectronic devices, such as integrated circuits, chips, processors, LEDs, lasers, transistors and solar cells, are made by depositing or growing very thin layers of atoms onto a semiconductor (or other material type) wafer substrate. During the thin film deposition/growth process, a batch of wafer substrates are heated from behind and rotated about a center axis in a vacuum environment. Direct benefits in end component quality and performance can be achieved by precisely controlling growth process properties like temperature and film thickness with high precision and repeatability.
Numerous methods have been disclosed for monitoring process temperatures and film thicknesses. These include precise and real-time monitoring of the substrate temperature or property. The BandiT™ system from k-Space Associates, Inc., Dexter Mich., USA (kSA), assignee of the subject invention, has emerged as a premier, state-of-the-art method and apparatus for measuring semiconductor substrate temperature. The kSA BandiT system is described in detail in US Publication No. 2005/0106876 and U.S. Publication No. 2009/0177432 the entire disclosures of which are incorporated hereby reference.
In addition to the use of sophisticated monitoring systems, the production of high-quality semiconductor products can be improved still further with advances in the deposition systems themselves that are used to create the formation of semiconductor nanostructures. In particular, in deposition systems that utilize a multi-wafer rotary platen, opportunities for improvement are manifest. Many such deposition systems lack a positive mechanical lock between the motor driven spindle and the platen, usually as a result of certain structural constraints or methods of sample transfer within those particular systems. Operative connection between the motor drive spindle and platen may be in the form of a magnetic or friction coupling rather than meshing gears or toothed belts. In these cases, the phase angle of the platen may over time drift from the initial spindle arbor phase angle, making the standard spindle arbor “home pulse” signal useless for synchronization. Or, the slippage may be more or less continuous such that the spindle drive system indicates a rotary speed of 1500 RPM for example, but in fact the platen is only spinning at 1480 RPM.
Such systems lack real-time synchronization between the diagnostic device(s), e.g., a temperature monitoring systems like the kSA BandiT and/or a film thickness measurement system, with the war samples in a multiple sample platen. This lack of synchronization can be more problematic in high speed spindle configurations, where rotation speeds above 1,000 RPM are not uncommon. Typically, in multiple sample platen deposition systems, the diagnostic device must spend many rotations to diagnose the locations of each measurement after they occurred, making real-time monitoring and eventual control impossible.
There is therefore a need for a system and method to overcome asymmetry issues with respect to platen and drive spindle for the purposes of improving quality and performance during the thin film growth process.